According to the French R&D organisation, the leading solid state approach for treating quantum information uses superconducting qubits, but it says other approaches are available. These include semiconductor spin qubits, previously demonstrated using III-V materials, which have a limited ‘lifetime’ due to coupling between the electron spin and the nuclear spins of the III-V elements.
Recently, work on isotopically purified silicon 28 has proved an attractive candidate, but CEA-Leti says the main challenge is to define an elementary cell compatible with circuit upscaling to hundreds of qubits.
Working with Inac, Leti is investigating an SoI approach developed originally for CMOS VLSI circuits. In this approach, quantum dots are created beneath the gates of n-type (respectively p-type) field effect transistors, which are designed to operate in the ‘few electron’ (respectively ‘few hole’) regime at temperatures of less than 0.1K.
According to the partners, they have developed a process for mastering control of the operation of both types of devices using Leti’s SOI nanowire FET technology. The team has demonstrated the co-integration and successful operation of quantum objects with standard ring oscillators on 300mm SOI substrates.
“This technology has acquired a certain degree of robustness and we aim at using it, with very minor modifications, to demonstrate qubits co-integrated with their control electronics,” said Louis Hutin, scientific staff. “This co-integration success represents a critical asset for the eventual design of a quantum computer.”
Meanwhile, the researchers say a qubit demonstration could be on the near horizon. The next step for the teams is to demonstrate a few coupled qubits and to develop a strategy for long range coupling of th
